In medical settings, an affected part of a human body or the like in internal organs, skeletons, and the like is photographed, for example, with X-rays for various tests and diagnoses. Through application of recent digital technology, a moving image in which movement of an affected part is captured with X-rays or the like can be acquired relatively easily.
In the recent digital technology, a dynamic image of a subject including a diagnosis target region can be photographed with use of a semiconductor imaging sensor such as a flat panel detector (FPD), enabling diagnosis through motion analysis of the diagnosis target region, which cannot be made in still image photographing and diagnosis by conventional X-ray photography.
In making diagnosis with use of moving images, moving images of the same subject photographed at different times, or moving images of different subjects may be compared with each other, for example. In such cases, it is difficult to simply compare a plurality of moving images because of a phase difference caused by a difference in photographing timing, and a difference in moving speed.
Technology for comparing a plurality of moving images for diagnosis has been proposed in recent years. For example, Patent Document 1. discloses technology of identifying, in moving image displaying technology, a phase of a target object in a series of dynamics, and rearranging frame images constituting a moving image in accordance with the identified phase to display the moving image. Specifically, when moving images of the chest from the front and from the side are displayed side by side, frame images constituting these moving images are rearranged to display these moving images so that phases in these moving images match each other.
Patent Document 2. discloses technology concerning a method of photographing, in radiographic image processing technology, an optical moving image at the same time as a radiographic moving image is photographed, and analyzing movements of test objects in optical moving images to display radiographic moving images so that movements of test objects in the radiographic moving images match each other. Specifically, frame images from which playback of radiographic moving images is started are determined based on movements of test objects, and display intervals between frame images are determined so that the movements of the test objects match each other. When a variation in display intervals between radiographic moving images is equal to or greater than a certain level, an interpolation image is inserted into a radiographic moving image.